Filament.



B. L. BENBOW.

FILAIVIENT.

APPLICATION FILED ocr. 4, 1913.

1,247,068. Pafented NOV. 20, 1917.-

]EYYEHTUR .BUHJYIE LEE EL'NB 01W, ay-

I H15 A2 TaRNEy.

UNITED STATES PATENT OFFICE.

BUB-HIE LEE BEITBOW, 0F CLEVELAND, OHIO, ASSIGNOB TO GENERAL EECTBIGcomm, A CORPORATION OF NEW YORK.

Specification 0! Le r a e I Patented NOV. 20, 191'? Application filedOctober 4, 1913. Serial No. 798,286.

Toallwhomitmaycmem."

Be it known that I, Bumnn LEE BENBOW,

a citizen of the United States, residing at Cleveland, -county ofCuyahoga, State of Ohio, have invented certain new and usefulImprovements in Filaments, of which the following is a. specification.

My invention relates to filaments for incandwcent lamps and moreparticularly to filaments of that character composed of metal such astungsten. The object of my invention is to produce a filament of ahighly concentrated form and of such consistency that it will requirecomparatively few supports in the lamp.

In producing my improved filament, I wind a straight fine filament wireof the roper diameter to produce the requisite 'ght under voltageconditions of the circuit in which it is to be used, into a coil orhelix of comparatively small diameter. The small diameter of the coilrenders the difference in otentialbetween successive turns when thefilament is in use very small and the wire may be wound with the turnsvery close together without danger of the current jumpintilzsrcrossbetween turns. The winding of coil is referably done on a mandrel ofquite sm diameter and the winding stres is such that the material isstressed be 0nd its elastic limit into a permanent h The filament thusproduced is then wound into another helix, the winding stress alsoexceeding the elastic limit of the material. This may be done on thesame mandrel upon which the first helix was wound. The result is whatmay be termed a double helix 0: a helix wound into a helix. In orderthat the turns of the second wound helix may be properly spaced fromeach other a spacing wire may be wound therewith and afterward removed.

In the drawing Figures 1 and 2 are views partially in sectlon showingtwo forms of incandescent lamp each containing a filament'embodying myinvention, and Fig. 3 is a detail view on an enlarged scale of a portion of the said filament.

The lamp shown in Fig. 1 has a filament consisting of a straight portion1 and a double helical portion 2. A support 3 composed of any metalcommonly used for supports and of such size that it is comparativelyrigid extends from the stem 4 into which it is sealed and is provided atthe tip and eyelet 6. The filament 1, 2 is twisted around the saideyelet and it extends from the same to the lead-in wires 7. It will bereadily seen that by this construction a considerable length of filamentmay be concentrated in a comparatively small length of lamp. Thisaflords a very useful construction especially where the lamp is to beused to illuminate show-cases and in other locations where it is desiredto direct a very brilliant light over a comparatively extensive area.

In Fig. 2 is shown a filament embodying my invention mounted in a lamphaving a spherical bulb 8. The filament 9 is concentrated around thecenter of the bulb and is draped between the supporting hooks 10 and 11which are mounted in the glass stem 12. Owing to the compact structureof the filament only a very few supports are required. Such a lampas-that shown in Fig. 2 is especially adapted for use where it isdesired to direct light by means of a reflector or reflecthereof withthe supporting hook 5 having tors to a comparatively small area. Lampsof this kind are especially adapted for use in connection withstereopticon apparatus, search lights, signal lights, and also forheadlights for vehicles.

In Fig. 3 is shown on an enlarged scale a section of a filamentembodying my invention. In mounting the filament it may be stretchedsomewhat. The process of winding, during which the wire is stressedbeyond its elastic limit, seems to increase its strength. The completedfilament is very elastic and may, be handled very roughly without dangerof breaking. After it is in use the filament sets and loses much of itselasticity. For this reason it is preferable not to stretch it inmounting; in other words, to wind it in substantiall which it will beused in the amp.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. In an electric incandescent lamp, a plurality of supports and a metallight emitting filament having the shape of a helix, the turns of whichare made 'up of helices, strlmg between the said supports, said filamentpossessing a permanent shape independent of said supports.

2. In an electric incandescent lamp, a li ht emitting filament havingthe shape 0 a helix, the turns of which are made up of helices, andmeans engaging only widely septhe shape in ereted portions of the saidfilament for supporting the same.

, 3. In an electric incandescent lamp, e light emitting filament haivinthe she e of e 5 helix, the turns of whic are me 0 up of helices.

4. In an electric incandescent lamp, a li ht emitting filament havingthe she e o a helix, the turns of which are med e up of 10 helices,saicl filament wire being support/e61 incense at only at few points inits length nndl being otalierwise free of contaict'with other meter]. s.

In witness whereof, l have hereunto set my henci this first clay of@ctoloer, 1913.

BURNIE LEE BENBOW.

